Not only does the group still conduct suicide bombings that have killed hundreds, but they’ve proved to be critical to the rebels’ military advance. In battle after battle across the country, Nusra and similar groups do the heaviest frontline fighting. Groups who call themselves the Free Syrian Army [FSA] and report to military councils led by defected Syrian army officers move into the captured territory afterward.

At least four bases have fallen to rebel forces in the last month, and Rebel commander Ali Jadlan told CNN that al-Nusra fighters were not only involved in the sieges but also responsible for the most dangerous area – the road to Aleppo.

Several dozen FSA in Damascus announced they that they had joined al-Nusra because of their fighting prowess. But others are very wary of the group and their Islamic ambitions, especially in the "liberated" northern areas where secular and jihadist rebel groups remove the safety on their guns as they pass each other's military bases.